class_docstr: Implements owners validation,pre load and post_load
  (to populate the owners field) on Marshmallow schemas
class_docstr_tok: ["Implements","owners","validation",",","pre","load","and","post_load","(","to","populate","the","owners","field",")","on","Marshmallow","schemas"]
code: def pre_load(self, data: dict[Any, Any]) -> None:
      # if PUT request don't set owners to empty list
      if not self.instance:
          data[self.owners_field_name] = data.get(
              self.owners_field_name, []
          )
  
file_path: superset/superset/views/base_schemas.py
imports: from collections.abc import Iterable, Mapping, Sequence
  from typing import Any, Optional, Union
  from flask import current_app, g
  from flask_appbuilder import Model
  from marshmallow import post_load, pre_load, Schema, ValidationError
  from sqlalchemy.exc import NoResultFound
  from superset.utils.core import get_user_id
label_desc: Use image node_id 2 for calling the BaseOwnedSchema obj's underlying member method code with example usage: obj.pre_load(data) without return types